Power-operated screw driver



Oct. 2, 1951 E H, SHAFF POWER-OPERATED SCREW DRIVER Filed Jan. 2, 194.7

omoo m Patented Oct. 2, 1951 POWER-OPERATED SCREW DRIVER Ernest H. Shaft', Spring Lake, Mich., assignor to Keller Tool Company, Grand Haven, Mich., a

corporation of Michigan Application January 2, 1947, Serial No. 719,803

7 Claims. 1

This invention relates to portable power driven tools such as screw drivers and nut runners, and has more especial reference to tools of this character which are actuated by air or other fluid pressure.

One object of the invention is to provide a portable power driven tool having a friction slip clutch drive for the tool spindle together with means accessible from the exterior of the tool for readily adjusting the pressure between the driving and driven members of the clutch.

Another object of the invention is to provide an air operated screw driver or nut runner having a suction device operative to pick up and retain the screws or nuts to be driven.

Yet another object is to provide an air driven tool having novel means by which the pressure of the tool on the work actuates a iiuid pressure inlet valve to the motor.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a longitudinal sectional view taken generally along the axis of a tool embodying the present invention.

Fig. 2 is a fragmentary plan view of the clutch adjusting means and showing in section the forward end of the tool in the operation of picking up a screw.

Figs. 3, 4 and 5 are transverse sectional views taken respectively along the lines 3 3, 4-4 and 5-5 of Fig. 1.

As illustrated in the drawings, the exemplary form of the invention is shown embodied in a portable pneumatic screw driver comprising a generally cylindrical main casing I0 having a rotary pneumatic motor II for driving a spindle I2 through the medium of a drive mechanism including a friction slip clutch I3. In the embodiment shown the front end of the spindle I2 is constructed for driving engagement into a screw driving bit I4.

The motor II comprises a casing formed by a sleeve I6 having` an eccentric opening therein and circular disks I1 and I8 abutting against flattened edges at opposite ends thereof, and a radially slidable vane type rotor I9 disposed for rotation between the disks. The rotor is mounted on a tubular drive shaft 20 extending axially through the rotor and projecting through the disks. The front end of the drive shaft is supported by a ball bearing 2| abutting the disk I1 and retained by an annular member 22 cast integral with. the disk l1. The other end of the (Cl. 14A-32) 2 shaft is supported by a ball bearing 23 abutting the disk I8 and retained in a counterbore 24 in a head 25 threaded into the housing at the end opposite the spindle.

The motor II is positioned in the casing I0 in spaced relation to the front end thereof so as to provide a chamber 2S for the friction slip clutch I3. Herein a sleeve 21 cast integral with the member 22 abuts an annular shoulder 218 in the casing. The head 25 screwed into the opposite end of the housing clamps the motor in position in the casing.

Pressure fluid is supplied to the motor I I under the control of a poppet type valve 29 axially slidable in a casing 30 disposed in the forward end of a bore 3| in the head 25. The rear end of the bore forms a chamber 32 to which air is supplied through a fitting 33 in the outer end of the head 25.

The valve 29 has a forward cylindrical portion or plunger 34 slidable in the casing 30, a rear head 35 for engagement with a seat 3B of the rear end of the casing 30, and an intermediate or shank portion 31 of reduced diameter so as to form an annular chamber 38 normally closed at its rear end by the valve head 35. Intermediate the ends of the casing radial ports 39 open into an annular groove 4D which in turn connects with an angular motor supply passageway having a radial portion 4I and a longitudinal portion 42. The latter registers at its forward end with an inlet port 43.

Air is exhausted from the motor casing through exhaust ports 44 in the disk I8 and thence through one or more axially extending passageways 45 in the head 25 to a chamber 46 and finally to the atmosphere through ports 41.

The tool spindle I2 is journalled in a spindle housing 54 of smaller diameter than and projecting from the main casing I0. Herein the spindle is in the form of a hollow shaft in axial alinement with the tubular drive shaft 2G and having its outer end shaped to form jaws 48 to loosely hold the bit I4 while permitting the passage of air about the latter member for a vpurpose which will presently appear. The forward end of the spindle is journalled in a sleeve 55 rigid with the spindle housing and forming a forward extension thereof.

The driving connection between the motor Il and the spindle I2 comprises in this instance a combined clutch and speed reducing mechanism disposed in the chamber 26 between the driving shaft 20 and the spindle l2.

This driving connection is of the type that permits slippage between the drive member and the driven member when a predetermined load is applied to the spindle. As shown it comprises cone-shaped members or rollers 56 mounted in planetary relation on a Spider 51 rigid with the spindle l2 and coacting with a cone-shaped drive member 58 rigid with the drive shaft 2S. The rollers are journalle'don pins 66 projecting axially toward the motor from the spider 51. As the rollers are caused to rotate about their respective axes by contact with the drive cone they are simultaneously caused to roll on-an internal-inclined surface 6l on the sleeve 21, the latter member being concentric with thedrivef cone.

An important feature of my invention residesy in the provision of means conveniently accessible from the exterior of the tool for varyingthe frictional pressure between the drive member and the driven member of the drive mechanism. In this instance, a compression spring 62 encircling Vthe spindle iris interposed between .an

adjustable abutment or collar 63 encircling the spindle, and afixed abutment'such as a ball thrust bearing 6G. The force exerted -by the spring istransmitted to the spider 51' through the thrust bearinggf, thereby urging the rollers 55 into frictional engagement with the taperedsurfacesof the drive cone S and the stationary sleeve 21.

Toadjust'the frictional pressure between the sur-faces of the frictionally engaged .members of the clutch mechanism, the tension of the spring urging the clutch members into engagementmay bechanged by varying the axial positionor" the collar S3. For this purpose, I provide means including asleeve or ring 55 conveniently accessible from the'exterior of the tool. The. ring encircles the outer end of the spindle housing and one end thereof abuts radial lugs 56 rigid with theA collar 6-3 and projecting through 1ongitudinally extending slots 61 in the spindle housing. At its other end the ring is constructed-to -form a nut S9 screw threaded upon thesleeve 55. VIt will be seen that by turning the-ring the position of the collar 63 mayv be varied thereby changing the tension of the spring.v

The spindleland its alined drive shaft are made hollow in order to provide a convenient control for the'motor responsive to the pressure :of the "tool on the work. As shown, the

control valve 29 is normally held against its Y valve seat 36 by air pressure in the chamberi 32, and is `opened bythe axial movement of a rod 1Q .which extends longitudinally through the hollowY drive shaft 2Q and through the hollow drive spindle i2. rear end of bit i4 andthe other end is secured to or integral with the valve plunger Se. Thus itcan be seen that as pressure is applied tof the spindle end of the tool, it will be transmitted through therigid rod to the plunger' thereby urging the head 35 axially away fromY the valvezseat-SS vto allow the passage of pressure fluid vto the'motor. Similarly the `removal of the pressure from the spindle end of the tool allows Vthe air pressure to again close the valve.

In accordance with my invention, the hollow Y drive shaft'and spindle are'also utilized to ad- One end of the rod abuts the 4 sageway 13 extending lengthwise of the head 25 and in communication with the exhaust chamber 46. It causes air to be sucked by Venturi action through a passageway 15 having one end in communication with a chamber 16 surrounding the nozzle 12.' The other end of the passageway 15 communicates with a chamber 18 formed'. at theinner end of thehead 25 bya counterboreconcentric with but of smaller dii ameter than the bearing retainer bore 24. The chamber 18 is in communication with an ani nularpassageway19 formed about the Valve operating rod 10 and extending through the tu bular driveSshaft-Z'land spindle l2.

Ashereinishow-n, the forward end of the tool is'constructedto provide a nder 80 for receiv- .ingrascrew'asair Ais drawn or sucked through the annular passageway 19. Herein the finder is-in= the form of a tube 8| encircling the bit I4 and in communication with the annular passagewayv 19. Tnetube'f'sl riseslidablyimountedlin' a tapered' nosepiece 82 1 threaded onlrthe sleeve'e-` 55,1` and-one end of the tuberhas arr'iannulariilange- 83 which .abuts `a `shoulder 181i?I on Lthe interioi Softhe nosepiece to prevent withdrawal therefrom; (The other f end of the `vtube vfisfrmedi 'tol receive round-*headed screws more readily.) Normally-, the kouter end of the tube isior'ced tof-protrude' beyond the end Aof the nosepiecelby-'alcompres sion spring 86. Thedatter encircles theibitan'd. is interposed be-ween the il'ange83Iandanabut#V ment in the form :ofiacollar 81 encirclirigthelbit, urging, .he flange into engagemen'tl with :the shoulder i The collar 81 additionally servestoprevent wi'hdrawal of the bit fromthe to01. Thus/it provides a stop -for"engagementbryfa shoulder 88? on theshank of the bit 14.

A needle valve 9i) in the-air supply'fchamberl 32 regulates the amount floflive-fair passing hrough the rnozzle 12 from the' chamber 32;' thereby controlling 'the amount of-suctien 'atthief nder end of the tool.V Herein 'the valve'is'disposed" transversely-of the .head and h'asia tape'red point or tip `Sil lcoactingfvvitllilla valv'e seat'SZ-Q The latter is formed -by iiaringthe innerendfdfl a radially extending passageway .93 connecting the chamber S32 with a chamber 94'at 'the rea-'rithe head Z5. 'I'his enlargementy provides "alsur face area onV which compressed airfsupplie'd'to the chamber 32 can actito-rnove'thevalve into`v open position.

Fcrconvenient adjustment of the 4vvalve rela-i tive toits seat, I provide a'ring91 encircling thiefhead 25 and having a ca'mjsurface'98 (I'ig15')VM for engagement with an exposed outer-end 99 of' the plunger 9'6; To openV the valvethe'ring 91V ig-rotated, permitting the endwof'he plungerto" be moved radially outwardlyr against the cir--v cular dwell surface of thering 91. Similarly,..t'o" close the valve,l the ring `is rotated to move-"the cam surface 98 into engagementfwith the en'clil' of the plunger to force the latter radially iiilg` ward. To guide the ringf'asthe'latter 'is 'rtated`," one end engages an annular-"shoulder '|00 on'tne head 25vwhile the opposite end abuts asplitri'ng I 0I mounted on the outer 'end'oftliefhea'd 25; Tol permit limited rotation of the atten'd rir'igtlie'f head A251s attened at I0 la'.

The operation of the tool will be;` apparent; from the foregoingvbut may be summarized 'as'l 7.5.'c

follows; Preparatory to using the "tool',"` the ring' 98 is turned to adjust the needle valve 90 so'that air will be discharged through the jet nozzle l2 thereby causing a suction of air throughithe annular` passage 'I9 and the nder 80. The nnder is then insertedinto a container having a supply of screws and upon contact with`the head end of the screw the suction at the finder end of the tool picks up and holds the screw in the proper position (Fig. l).

With the screw thus held applied to the work endwise pressure is applied to the tool, causing the finder to telescope into the nosepiece 82, thereby bringing the bit into engagement with the head of the screw as shown in Fig. 2. Additionally, pressure on the finder urges the rod 'l0 axially rearward to open the valve 29, thereby admitting air to the motor to drive the tool spindle. So long as valve 9B remains open suction will be produced in the nder so as to render the latter effective to pick up screws.

When the driving torque on the screw has exceeded a predetermined maximum, the clutch drive I3 will slip so that the tool spindle will come to rest. The amount of torque to be applied to the screw can be quickly and easily changed by turning the adjusting ring 65, which is readily accessible from the exterior of the wool, thereby varying the tension on the spring 62.

I claim as my invention:

1. A portable pressure iluid operated tool having, in combination, a motor, a hollow spindle driven by said motor, a spindle housing, a nder for threaded elements to be driven, said finder being slidably mounted in said spindle housing, a valve controlling the flow of pressure fluid to said motor, a rigid member extending through said hollow spindle and forming therewith an annular passageway in communication with said finder, said member having one end operatively associated with said finder and the other end engaging the valve whereby axial pressure on the member will shift said valve, a chamber communicating with said finder through said annular passageway, and means for sucking air from said chamber.

2. In a pneumatic tool, the combination of a main housing, a pneumatic motor having a hollow drive shaft in said housing, a hollow spindle driven by said drive shaft, a spindle housing projecting from said main housing, a finder mounted for axial movement on said spindle housing and in axial alinement with said spindle, said drive shaft and spindle forming a passageway communicating with said nder, and means for yproducing suction on said finder including an air passage communicating with a source of air under pressure, a second passage leading from the first passage and connecting with said passage- Way to the finder, and an ejector nozzle in the first passage operative in the discharge of air therethrough to eifect a withdrawal of air from the second passage.

3. In a portable pneumatic tool having a motor, means defining an air supply chamber for connection with a source of compressed air and communicating with said motor, a spindle driven by the motor, a tool on the spindle, a iinder for threaded elements encircling the tool and open at its forward end, and means including an ejector for producing a suction on said iinder, said ejector including a nozzle, an air supply chamber for the nozzle, and manually operable valve means controlling the supply of air from said motor supply chamber to said nozzle supply chamber including a member shiftable into different `positions and acting in one of said 'positions to permit air .pressure in said motor supply chamber to hold said valve means open and acting in another of said positions to hold said valve means closed.

4. In a portable pneumatic tool having a casing, a motor in the casing, said casingr defining an air supply chamber for said motor, a spindle driven by the motor, a tool on the spindle, a finder tube encircling the tool, ejector means for p'roducing a suction on the finder tube including 'a nozzle, an air supply chamber for the nozzle, a valve movable radially of the casing and controlling the delivery of air lfrom said motor supply chamber to said nozzle supply chamber, and a rotary cam sleeve on said casing s hiftable into different positions, said cam sleeve being operative in one of said positions to hold said valve closed and in another of said positions to permit opening of said valve.

5. In a pneumatic tool, the combination of a housing, a rotary driving motor in said housing having a drive shaft with an axial bore therethrough, a tool spindle forwardly of the drive shaft and having an axial passage communicating with said bore, a driving connection between said shaft and said spindle, a finder for threaded elements providing a forward suction nder chamber communicating with the forward end of said spindle passage, a driver for threaded elements slidable in said finder and having a driving connection with said spindle operative to permit the passage of air from said forward suction chamber to said spindle passage, valve means controlling the flow of pressure fluid to the motor and including a shifta'ble valve member, a rear suction chamber communicating with the rear end of the bore in the drive. shaft, means operable upon admission of pressure iluid to the motor under control of said valve means to produce a suction in said chamber, and a motion-transmitting member interposed between said driver and said valve member and extending through the axially alined passage and bore in the spindle and drive shaft respectively whereby axial pressure applied to said driver may be transmitted to said valve member, said member being dimensioned with respect to the passage and the bore to permit the flow of pressure fluid between said chambers.

6. In a pneumatic tool, the combination of a motor, valve means controlling the supply of pressure fluid to said molor, a spindle driven by said motor, a spindle housing, a finder for threaded elements to be driven comprising a, tube mounled for movement axially of said housing and normally open at one end for the reception of the head of a threaded element to be driven, means operative to exhaust air from said tube so as to cause such threaded element to adhere to the normally open end thereof, and means operative as an incident to the movement of said finder relative to said spindle housing to actuate said valve means including a valve operating member movable axially of said spindle.

7. A portable pressure fluid operated tool comprising, in combination, a pressure fluid operated motor, a tool spindle driven by the motor, a finder for threaded elements providing d chamber normally open at one side for the reception of a threaded element, valve means for controlling the supply of airto said motor including a supply chamber, and means including an ejector rendered operative upon the supply of air to said mber.

supyfehmber to exhaust airffrom said nder ERNEST H. SHA-FF:

REFERENCES CTTD Number Name Y Date K Risser 1 1 1 7 1 Mar. 4, 1930 Nuber f' sf Name D21/t'- La; Sept. 22, 1931V Snyder: Aug. 17, 1943 

